U.S Pat. No. 3,801,875, entitled "Non-Metallic Load Center With Improved Bus Bar Construction", describes a molded plastic load center wherein the plastic case includes circuit breaker and branch strap mounting means integrally formed therein. The insulative properties of the plastic allows the circuit breakers to be compactly arranged without fear of electrical breakdown between the breakers or the terminal connections. The circuit breaker branch straps are mounted on the bottom surface of the plastic enclosure. Access to the terminal connections is made by unscrewing the cover from the case and lifting the cover away from upstanding tabs integrally formed within the case.
U.S. patent application Ser. No. 874,755, filed June 16, 1986, entitled "Molded Plastic Enclosure For Electric Service Apparatus", describes one such enclosure including an access door mounted on the cover for convenient access to the circuit breakers contained therein. A locking hasp is integrally formed on the door for padlocking the door against unauthorized access.
U.S. patent application Ser. No. 811,716, filed Dec. 20, 1985, entitled "Molded Plastic Enclosure For Disconnect Switches", wherein an access door is formed within the cover and hasp means are integrally formed within the cover for the arrangement of a padlock to prevent unauthorized access. The switches contained within the enclosure are of the type used with air conditioning disconnects. Both aforementioned patent applications are incorporated for reference purposes and should be reviewed for a good description of the relationship between the molded plastic door, cover and case used for housing both circuit breakers and electric switches.
Although non-metallic load centers have found limited application over the past few years, wide market acceptance has not, as yet, been realized mainly due to the lower cost of comparable metallic load centers as well as the ease afforded in mounting the metallic load centers to support walls. An explosive charge-driven tool or "stud gun" has not heretofore been used with plastic load centers because of the fracturing of the plastic caused by the radial tensile forces on the plastic material at the sides of the driven nail as well as the compressive forces applied to the plastic material under the drive nail head.
U.S. patent application Ser. No. 026,503, filed 3/16/87 entitled "Compact Non-metallic Electrical Load Center Enclosure", describes the use of a shaped metal cap inserted within openings formed through the bottom of a plastic load center enclosure to allow the use of an explosive charge-driven tool to flush-mount the enclosure to a support wall. This application is incorporated herein for purposes of reference and should be reviewed for its teachings of the plastic resin materials used to form injection molded plastic enclosures. In some applications, the enclosure must remain water tight such that such openings are not permitted. In other applications, some cooling space is required between the enclosure and the support wall, such that flush-mounting is not allowed.
One purpose of the instant invention is to describe a molded plastic enclosure for electrical equipment such as switches, meters and breakers wherein the three plastic enclosure components are formed on automated equipment and wherein the metallic components are inserted by means of a completely automated process. It has since been determined that the savings realized by complete automation results in a molded plastic circuit breaker enclosure that is less expensive than comparable metallic circuit breaker enclosures. Another purpose of the instant invention is to describe a means for attachment of non-metallic electrical enclosures which also provides increased thermal capacity to the interior of the enclosure.